The attainment of satisfactory results with any fluidized bed apparatus depends, of course, upon the provision of an adequate supply of coating material in all operative portions of the fluidization unit; generally, the maintenance of a uniform, predetermined level of powder is also of significant importance. In many instances, practical operation demands that the supply be replenished automatically, but difficulties have been encountered in accurately correlating the feed function to the true requirements of the system.
Accordingly, it is an object of the present invention to provide a novel fluidized bed coating system in which the replenishment of coating material in the fluidized bed is accurately correlated to actual need.
It is also an object of the invention to provide such a system in which the level of fluidization is automatically maintained fairly constant and uniform within the coating unit.
Another object of the invention is to provide such a system in which the fluidized bed unit is elongated.
Still another object is to provide an electrostatic coating system having the foregoing features and advantages.
A further object is to provide a system in which such control of the powder supply is simply and yet effectively achieved.